Impulse voltage testing equipment



Jan. 2, 1940.

G. L. CANDLER ET AL IMPULSE VOLTAGE TESTING EQUIPMENT Filed Aug. 13, 1938 2 Sheets-Sheet WITNESSES:

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IMPULSE VOLTAGE TESTING EQUIPMENT Filed Aug. 13, 1938 2 Sheets-Sheet 2 /Z4 /Z5 /Z6 0 flea /Z4 A?! /Z6 95 /95 99 WITNESSES: INVENTOR 97201 MM George A. [and/ er 6 fl/bry/n.

Patented Jan. 2,1940

UNITED, STATES IDIPULSE VOLTAGE TESTING EQUIPMENT George L. Candler and William D. Albright,

Sharon, Pa., assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application August 13, 1938, Serial No. 224,704

7 Claims.

Our invention relates to impulse voltage testing of electrical apparatus in which a surge generator is employed in connection with a cathode ray oscillograph for recording surge characteristics,

such as voltage.

In testing the impulse voltage strength of insulating material employed in electrical apparatus and recording the surge Wave, it is necessary to initiate the discharge of the surge generator at a very definite time with respect to the operation of the timing circuit of the oscillograph. In order to accomplish the correct timing'of the surge generator throughout its operating range, it has been found that the initiating voltage applied to the surge generator tripping circuit should be relatively highfcr example, 60 kilovolts or more.

The initiating condenser that controls the discharge of the surge generator and initiates the operation of the oscillograph timing circuit may be charged from the same direct current supply source as the cathode of the oscillograph. The voltage of this supply source is, in many cases, fixed by the operating conditions of the oscillograph at a voltage below that required for the surge generator initiating condenser, such, for example, as at a value in the neighborhood of 37 kilovolts.

It is an object of our invention to provide a method and means for coordinating the initiation of the discharge of a surge generator with the operation of an oscillograph.

It is a further object of our invention to provide a common source of supply of direct current energy for supplying the cathode of the oscillograph and for supplying current to the circuits for initiating the operation of the surge generator and the oscillograph.

Other objects and advantages of our invention will be apparent from the following description of certain preferred embodiments thereof, reference being had to the accompanying drawings, in which:

Figure 1 is a diagrammatic view of circuits and apparatus organized in accordancewith our in- V vention for employing a negative initiating surge to trip the surge generator and oscillograph;

Fig. 2 is a diagrammatic view illustrating a portion of the circuits and apparatus illustrated in Fig. l with the tripping switch in its discharging position;

Fig. 3 is a diagrammatic view of a portion of the circuits and apparatus ,used in the system of Fig. 1 arranged for delivering a positive initiating surge to trip the surge generator and oscillograph;

66 and Fig. 4 is a diagrammatic View of the circuits and apparatus illustrated in Fig. 3 with the tripping switch in its discharging position.

Referring to Fig. 1 of the drawings, the condensers I, 2, 3 and 4 illustrate the capacitor ele- 5 ments of a surge generator arranged to discharge in series through spheres 5, 6, I, 8, 8, H), H and I2 to deliver a surge voltage to conductor I3 and through the gap represented by spheres I4 and I5 and conductor I6 to the apparatus being tested. 10

Such apparatus is illustrated as a transformer l1, having a primary winding l8 connected between the conductor 16 and ground at l9, and a secondary winding 20 connected between conductors 2| and 22. A load resistor 23 is connected between 15 conductor l3 and ground at 24, to which point one side of the condenser I is illustrated as grounded throughconductor 25. Theseveral condensers I,

2, 3 and 4 are arranged to be charged in parallel from a source of direct current energy repre- 20 sented by conductors 3| and 32. Resistors 33, 34, 35 and 36 are connected in series with conductor 3| between the terminals of the various condensers or group of condensers l, 2, 3 and 4, and similar resistors 31, 38 and 39 are connected in series with conductor 32 between the terminals of the various groups of condensers connected to that conductor. 1

A cathode ray oscillograph is diagrammatically illustrated including an emission tube 42, having a cathode 4| and an anode 43 connected to ground at 44, a relay part 45 and a recording part 46. The relay part 45 includesa target 41 against which the cathode ray beam, represented by the dotted line 48, strikes and is intercepted when the oscillograph is not recording. The cathode ray beam is bent about the target 4'! as illustrated by the dotted line 48 upon the energization of the plates 50, 5!, 52, 53, 54, 55, 56 and 51 when energized in accordance with. the operation of the oscillograph timing circuit indicated generally at 58.

The recording part of the oscillograph includes a pair of deflecting plates 59 connected by conductors 62 and 63, respectively, to be energized from the timing system circuit 58, and a pair of deflecting plates 64 connected by conductors 65 and 66 to be energized in accordance with some chosen fraction of the voltage drop across a potential dividing resistor 6! connected between con- 50 ductor I3 and ground at 68.

The timing system 58 includes two half-wave rectifier tubes 12 and 13 connected for charging condensers Hand 15, respectively, that are connected to opposite ends of a resistor 16, the midpoint 11 of which is connected to ground at 18 and through the secondary winding 19 of a transformer to the common conductor 82 between the tubes 12 and 13. A primary winding 83 is inductively related to the transformer winding 19 through which alternating current energy is supplied to the timing circuit. The tubes 12 and 13 maintain the condensers 14 and 15 charged continually to substantially peak alternating current voltage with the flow of a very small current so that during the charging operation substantially no voltage exists across the re-' sistor 16. The plates 50, 53, 55 and 56 of the relay part of the oscillograph are connected by conductor 84 to a selected point on the resistor 1'6, and the plates 5|, 52, 54 and 51 are connected by conductor 85 to another selected point on the resistor 16, so that upon discharge of the condensers 14 and 15 a predetermined voltage will appear across resistor 16 a portion of which will be applied between pairs of relay plates. Likewise, one of the deflecting plates 59 is connected through conductor 62 and resistor 86 to a selected point on the resistor 16, and the other of the pair of plates 59 is connected through conductor 63, resistor 81 to a selbted point on the resistor 16. An adjustable condenser 88 is connected between resistors 86 and 81 for adjusting the voltage to be applied across deflector plates 59.

The anode of tube 12 is connected by conductor 89 to a sphere 92, and the cathode of tube 12 is connected by conductor 93 to a sphere 94. A common tripping circuit for tripping the surge generator and the timing system 58 of the oscillograph is provided including a conductor 95 that is connected to a sphere 96 through a resistor 91, the sphere 96 being positioned between spheres 5 and 6 of the surge generator. The conductor 95 is connected to ground at 98 through a high resistor 99 from an intermediate, point of which a conductor I02 connects to a sphere I03 positioned between the spheres 92 and 94 of the oscillograph timing system.

In order to provide a source of rectified current for the oscillograph emission tube 42, a rectifier tube I04 is provided connected in a circuit extending from ground at I05'through a secondary transformer winding I06, a resistor I01, conductor I08 that is connected to the oscillograph cathode 4|, a condenser I09 and conductor IIO to the grounded side of the winding I06. Alternating current energy is supplied at low voltage to the primary winding H2 for energizing the rectifier circuit which supplies a nega tive potential of, say, 31 kilovolts to the oathode 4 I In order to provide an initiating condenser assembly of the proper voltage for effecting the desired simultaneous operation of the surge generator and the oscillograph timing circuit to de liver either a positive or a negative initiating surge from a fixed source of negative polarity, condensers H4 and H5 are provided. A resistor H6 is connected between terminals of one polarity, and a resistor H1 is connected between terminals of opposite polarity of the condensers H4 and H5.

In Figs. 1 and 2, the condensers are connected for supplying a negative surge to the tripping circuit, and, as illustrated, the positive terminal of condenser II 5 is connected to ground at H8, and the negative terminal of the condenser H4 is connected to a sphere H9 which, together with a sphere I22, forms a gap between the initiating condenser circuit and the tripping circuit that is set so that it will not break down upon the application of voltage thereacross corresponding to that supplied from the tube I04 to the condensers H4 and H5 in parallel. The negative terminals of the condensers H4 and H5 are connected through conductor I23 and switch contact members I24 and I25 in the position illustrated in Fig. 1, and a charging resistor I26 to conductor I08 constituting a negative potential source through which condensers I I4 and I I5 are charged in parallel.

The resistors H6 and H1 serve as charging resistors to prevent excessive initial drain of energy from the cathode supply rectifier during charging of condensers H4 and H5. These resistors, which are of high ohmic value, perform a secondary function of preventing short circuiting of the condensers H4 and H5 when discharged in cascade, as will be shortly described.

After the condensers H4 and H5 have been charged by the parallel flow of current from conductor I23 to ground at H8, and it is desired to initiate operation of the surge generator and of the oscillograph, the switch contact member I24 is moved toward the left into engagement with the switch contact member I28 to connect the negative terminal of condenser II5 to the positive terminal of condenser II4 through contact members I24 and I28 and conductor I29, as shown in Fig. 2, thus applying a voltage across the gap between spheres H9 and I22 corresponding to the sum of the voltages of condensers H4 and H5, causing the gap to break down. Upon breakdown of this gap, the tripping circuit including conductor 95, which is normally at ground potential, is raised to a potential corresponding to the voltage drop across resistor 99, thus increasing the potential between sphere gaps 96 and 6 of the surge generator to a value high enough to effect a spark discharge thereacross. Upon the flow of current across this gap, the entire voltage of the condenser I that is normally applied between spheres 5 and 6 appears between spheres 5 and 96, causing this gap to break down, thus connecting condensers I and 2 in series between spheres 1 and 8 to cause this gap to break down. In a similar manner the successive gaps between spheres 9 and I0, and II and I2 break down to apply the full charge of the surge generator between conductor I3 and ground. The gap between spheres I4 and I5 breaks down to apply this voltage across the transformer winding I8 in a well known manner.

Simultaneously, with the breakdown between gaps M9 and I22, a portion of the voltage across resistor 99 appears on the sphere I03, which is so adjusted that the gap between spheres 94 and I 03 initially breaks down, thus bringing the combined voltages of condensers 14 and 15 across the remaining gap between spheres 94 and I03, which is so adjusted as to break down and cause the condensers to discharge across this gap between spheres 92 and 94 and impress a high voltage across resistor 16. This voltage is employed for simultaneously operating the oscillograph relay 45 and impressing a voltage between deflecting plates 59 for causing the cathode beam 48 to be moved across the film at a substantially uniform velocity at the same time that voltage is impressed between deflection plates 64 for varying the position of the beam 48 at right angles to its direction of substantially uniform velocity in accordance with the magnitude of the transient being recorded.

It will be seen from theabove description that when the switch contact I24 is moved from its charging position, in engagement with contact I25, to its discharging position, in engagement with the contact I28, the voltages of the two condensers are added, the positive terminal of the series connection being grounded at I I8, and the negative terminal of the series connection being connected to the sphere H9. This series potential causes the gap between spheres H9 and I22 to spark over and initiate simultaneous discharge of the surge generator and the oscillograph timing circuit. The gap between spheres I I9 and I22 prevents the resistor 99 from becoming a load on the cathode supply source during charging of the condensers H4 and H5.

For initiating a positive surge, the condensers II 4 and H5 are connected as shown in Figs. 3 and 4, the negative terminalsof the condensers being connected to the negative conductor I08 of the cathode supply source in the. same manner as in Fig. 1. In this case, however, the spheres H9 and I22 are not employed, nor is the ground connection shown in Figs. 1 and 2 employed. The tripping circuit conductor 95 is connected to the positive terminal of the condenser H5, and the negative terminal of the condenser H4 is connected to a sphere I32 which together with sphere I33, forms a gap connection to ground at I34. The resistor 99 in this case serves as a charging resistor between the positive terminals of the condensers I I4 and I I5 and ground. Upon movement of the switch contact member I24 to its discharged position, as shown in Fig. 4, a circuit is completed from the positive terminal of condenser H5 that is initially at ground potential due to the connection through resistor 99 through condenser H5, conductor I23, switch contact members I24 and I 28, conductor I29 and condenser H4 to impress a voltage between spheres I32 and I33 corresponding to the sum of the voltage of condensers H4 and H5, causing this gap to break down and supply a positive initiating surge to the surge generator through conductor 95 and to the timing system circuit of the oscillograph through conductor I02 to cause simultaneous operation of the surge generator and of the oscillagraph, as above described for a negative initiating surge.

Many modifications of the apparatus and circuits illustrated may be made within the spirit of our invention, and we do not wish to be limited otherwise than by the scope of the appended claims.

We claim as our invention:

1. In combination,.an impulse generator comprising a parallel charging circuit. and a series discharging circuit, a cathode ray oscillograph comprising an emission tube including a cathode, a relay part with a recording part, a timing system for controlling said relay and recording parts, a high voltage direct current supply source connected to said cathode, and means for simultaneously initiating the discharge of said surge generator and the operation of said oscillograph timing system comprising a common tripping circuit, a pair of spaced spheres forming a sphere gap, a plurality of condensers adapted to be connected to said cathode supply source through a parallel charging circuit and to the tripping circuit through a series discharge circuit including said sphere gap.

2. In combination, an impulse generator comprising a parallel charging circuit and a series discharging circuit, a cathode ray oscillograph comprising an emission tube including a cathode, a relay part and a recording part, a timing system for controlling said relay and recording parts, a high voltage direct current supply source connected to said cathode, a common tripping circuit including a sphere for initiating the discharge of said surge generator and a sphere for initiating the operation of said oscillograph timing system, a plurality of condensers, switching means for connecting said condensers to said cathode supply source through a parallel charging circuit andto said common tripping circuit through a series discharge circuit.

3. In combination, an impulse generator comprising a parallel charging circuit and a series discharging circuit, a cathode ray oscillograph comprising an emission tube including a cathode, a relay part and a recording part, a timing system for controlling said relay and recording parts, a high voltage direct current supply source connected to said cathode, a common tripping circuit for said surge generator and said oscillo graph timing system, a pair of spaced spheres forming a sphere gap, a plurality of condensers, switching means effective in one operative position to connect said condensers in parallel relation to said cathode supply source and in another operative position to connect said condensers in series relation to said common tripping circuit through said sphere gap.

4. In combination, an impulse generator comprising a parallel charging circuit and a series discharging circuit, a cathode ray oscillograph comprising an emission tube including a cathode, a relay part and a recording part, a timing system for controlling said relay and recording parts, a high voltage direct current supply source connected to said cathode, a common tripping circuit for said surge generator and said oscillograph timing system, a plurality of condensers, high resistance impedance devices connected between corresponding terminals of said condensers, a terminal of one of said condensers being connected to ground, switching means for connecting the opposite terminal to the cathode supply source for charging in parallel, a sphere gap between a terminal of one of said condensers and said tripping circuit, and switching means for connecting said condensers in series circuit relation to discharge across said gap.

5. In combination, an impulse generator comprising a parallel charging circuit and a series discharging circuit, a cathode ray oscillograph comprising an emission tube including a cathode, a relay part and a recording part, a timing system for controlling said relay and recording parts, a high voltage direct current supply source connected to said cathode, a common tripping circuit for said surge generator and said oscillograph timing system, a plurality of condensers, high resistance impedance devices connected between corresponding terminals of said condensers, a terminal of one of said condensers being connected to said tripping circuit, a terminal of one of said condensershaving a polarity opposite to the above-named terminal being connected to a sphere gap the opposite side of which is connected to ground, switching means for connecting the terminals of said condensers corresponding in polarity to that connected to said sphere gap to the cathode supply source for charging in parallel, and means for connecting said condensers in series with said sphere gap to effect a discharge thereacross.

6. In combination, an impulse generator comprising a parallel charging circuit and a series discharging circuit, a cathode ray oscillograph comprising an emission tube including a cathode, a relay part and a recording part, a timing system for controlling said relay and recording parts, a high voltage direct current supply source connected to said cathode, a common tripping circuit for said surge generator and said oscillo- -graph timing system, a plurality of condensers,

ammo:

comprising an emission tube including a cathode, a relay part and a recording part, a timing system for controlling said relay and recording parts, a high voltage direct current supply source connected to said cathode, a common tripping circuit for said surge generator and said oscillograph timing system, a plurality of condensers, corresponding terminals of said condensers being connected to said tripping circuit and to a ground,

connection therein, a terminal of one of said condensers having a polarity opposite to the above named terminals being connected to a sphere gap the opposite side of which is connected to ground, switching means for connecting the terminals of said condensers corresponding in polarity to that connected to the sphere gap to the negative terminal of the cathode supply source for charging in parallel, and switching means for connecting said condensers in series between said tripping circuit and said sphere gap to discharge thereacross.

GEORGE L. CANDLER. WILLIAM D. ALBRIGHT. 

